Changes in the benthic fauna and flora after application of temephos to a stream on Mt. Tsukuba

A dose of 2 ppm of temephos in emulsifiable formulation was applied to a mountain stream to observe its effects on the zoobenthos and the subsequent changes in benthic algae. Most zoobenthos in the treated region drifted but there were slight differences among taxa. Ephemeroptera and Plecoptera disappeared but some Trichoptera and Diptera survived. Chironomids recolonized earlier than other invertebrates and reached a higher density level than before the treatment. A bloom of benthic algae occurred following the destruction of fauna. The increase in the standing crop of algae was accompanied by an increase in the number of species. Among these, Achnanthes lanceolata, Meridion circulare and Tetraspora gelatinosa were predominant. The end of the bloom began with the recovery of the zoobenthos population.